Supporting apparatus are used in the manufacture of tubular films of thermoplastic materials in tubular film blowing plants, and are connected to the extruder so as to guide and support the initially soft plastic tubular film emerging from its ring nozzle until the plastic is sufficiently solidified and cooled, so that the tubular film, which is usually withdrawn by means of a pair of rolls, can be laid flat and fed to a film winder. The external support of the tubular film by groups of supporting segments disposed successively in the direction of withdrawal, which preferably cooperate in a ring to support the tubular film with the correct diameter, enables cooling air to come externally in direct contact with the surface of the tubular film that is to be cooled, in order thus to have a favorable influence on the solidification of the plastic material and the strengthening of the plastic film.
In practice, however, this desired kind of action is made difficult to achieve by complicated adjusting mechanisms which are necessary for the purpose of adapting the supporting segments of all supporting segment groups by simultaneous adjustments of the same kind to the different tubular film diameters which are being produced in the tubular film blowing facility according to product requirements. For example, in a known supporting apparatus of the kind specified above, the bars which hold the supporting segments are disposed about halfway between the succeeding turning bars in the circumferential direction, in that each individual supporting segment is joined at its one end to the corresponding turning bar and at the other end to the corresponding holding bar. This not only results in a great mechanical complexity, but also the free access of the cooling air to the outside of the tubular film is considerably impaired under certain circumstances by the great number of the turning bars and holding bars running in the direction of withdrawal of the tubular films, whose number is determined by the number of individual supporting segments used in each group of supporting segments.